Sans

The once loved skeleton from all across the underground, who brought cheer and laughter to those who need it has now turned into a sick twisted creature, who annihilates any creature entering his territory.

The once fun and childish traps that he’s brother, made have now been turned into slaughterhouses draining the victim of any energy, to escape keeping them alive and fresh ready for harvesting by their creator.

Sans mind has been completely shattered physically and mentally due to that flower, after that event sans depression grew into psychotic depression usually hearing the voices of the monsters, pleading to be spared or there screams as their throats are slit.

When the first stage of “the feast” ended sans knew he couldn't use bone attacks, so using the spine of a deceased animal and bits of metal, he made his bone scythe and thanks to this weapon monsters started calling sans, “the reaper” due to how it would take one strike to kill his victim.

The last time sans summoned a gaster blaster, it was his last when the creatures popped into reality they would scream in pain, then attack the first creature they see even sans, and when sans saw this he knew he could never let them return again.

Beast sans
This is what happens when sans loses control, a beast which was designed to kill this creature doesn't know mercy, or anything besides to kill and devour not even the strongest monsters, in the underground could stop he’s rampage if you ever hear he’s roar echo through the forest, just hope he doesn't find you….